1. Technical Field
The present disclosure relates to sodium secondary batteries.
2. Description of the Related Art
The abundant resource of sodium metal makes sodium secondary batteries attractive as next-generation batteries to replace lithium secondary batteries. Sodium secondary batteries are still on the way of development. For example, sodium secondary batteries compare unfavorably to lithium secondary batteries in terms of energy density. It is therefore demanded that the energy density of sodium secondary batteries be enhanced.
N Yabuuchi, et al. (Nature Materials 11, 512-517, 2012) discloses that a sodium secondary battery containing P2-type Nax[Fe1/2Mn1/2]O2 as a positive electrode active material realizes a capacity density of 190 mAh/g.
International Publication No. WO 2010/109889 discloses saturated cyclic ester carbonates and mixtures of saturated cyclic ester carbonates with saturated chain ester carbonates for use as non-aqueous solvents in non-aqueous electrolytic solutions for sodium secondary batteries.
Japanese Unexamined Patent Application Publication No. 2010-165674 discloses electrolytic solutions which include organic solvents having nitrile groups.